High tertiary amine content compositions useful as polyurethane catalysts

ABSTRACT

Covers compounds of the formula ##STR1## where R&#34; is lower alkyl, R is hydrogen or lower alkyl and Y is selected from the group consisting of CN, CONH 2 , CO 2  R&#39;, CONR&#39; 2  and COR&#39; where R&#39; independently is hydrogen, lower alkyl or aryl. Also covers a method of producing a polyurethane by utilizing said above compounds as catalysts in reacting an organic polyisocyanate with an organic polyester polyol or polyether polyol in the presence of said catalyst.

This is a division, of application Ser. No. 766,464, filed Feb. 7, 1977now abandoned which in turn is a division of Ser. No. 733,548, filedOct. 18, 1976 now U.S. Pat. No. 4,049,591.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention pertains to the field of urethane catalysts. Moreparticularly, this invention relates to the use of certain amines asurethane catalysts.

2. Description of the Prior Art

The use of a catalyst in preparing polyurethanes by the reaction of apolyisocyanate, a polyol and perhaps other ingredients is known. Thecatalyst is employed to promote at least two, and sometimes three majorreactions that must proceed simultaneously and competitively at balancedrates during the process in order to provide polyurethanes with thedesired physical characteristics. One reaction is a chain extendingisocyanate-hydroxyl reaction by which a hydroxyl-containing molecule isreacted with an isocyanate-containing molecule to form a urethane. Thisincreases the viscosity of the mixture and provides a polyurethanecontaining secondary nitrogen atom in the urethane groups. A secondreaction is a cross-linking isocyanate urethane reaction by which anisocyanate-containing molecule reacts with a urethane group containing asecondary nitrogen atom. The third reaction which may be involved is anisocyanate-water reaction by which an isocyanate-terminated molecule isextended and by which carbon dioxide is generated to blow or assist inthe blowing of the foam. This third reaction is not essential if anextraneous blowing agent, such as a halogenated, normally liquidhydrocarbon, carbon dioxide, etc., is employed, but is essential if allor even a part of the gas for foam generation is to be generated by thisin-situ reaction (e.g. in the preparation of "one-shot" flexiblepolyurethane foams).

The reactions must proceed simultaneously at optimum balanced ratesrelative to each other in order to obtain a good foam structure. Ifcarbon dioxide evolution is too rapid in comparison with chainextension, the foam will collapse. If the chain extension is too rapidin comparison with carbon dioxide evolution, foam rise will berestricted, resulting in a high density foam with a high percentage ofpoorly defined cells. The foam will not be stable in the absence ofadequate crosslinking.

It has long been known that tertiary amines, such as trimethylamine,triethylamine, etc., are effective for catalyzing the secondcrosslinking reaction. Other typical tertiary amines are set forth inU.S. Pat. Nos. 3,925,268; 3,127,436; and 3,243,389 and German OLS Nos.2,354,952 and 2,259,980. Some of the tertiary amines are effective forcatalyzing the third water-isocyanate reaction for carbon dioxideevolution. However, tertiary amines are only partially effective ascatalysts for the first chain extension reaction. To overcome thisproblem, the so-called "prepolymer" technique has been developed whereina hydroxy-containing polyol component is partially reacted with theisocyanate component in order to obtain a liquid prepolymer containingfree isocyanate groups. This prepolymer is then reacted with additionalpolyol in the presence of a tertiary amine to provide a foam. Thismethod is still commonly employed in preparing rigid urethane foams, buthas proven less satisfactory for the production of flexible urethanefoams.

For flexible foams, a one-step or "one-shot" process has been developedwherein a tertiary amine, such as triethylenediamine, is employed inconjunction with an organic tin compound. Triethylenediamine isparticularly active for promoting the water-isocyanate reaction and thetin compound is particularly active in synergistic combination with thetriethylenediamine for promoting the chain extension reaction. However,even here, the results obtained leave much to be desired.Triethylenediamine is a solid and must be dissolved prior to use toavoid processing difficulties. Also, triethylenediamine and other of theprior art amines can impart a strong amine odor to the polyurethanefoam.

In addition to problems of odor and handling due to solid character,other tertiary amines suffer still further deficiences. For example, insome instances the compounds are relatively high in volatility leadingto obvious safety problems. In addition, some catalysts of this type donot provide sufficient delay in foaming, which delay is particularlydesirable in molding applications to allow sufficient time to situatethe preform mix in the mold. Yet other catalysts, while meetingspecifications in this area do not yield foams with a desirabletack-free time.

Lastly, while certain tertiary amines are somewhat suitable in thiscatalytic area, they nevertheless do not have a sufficiently hightertiary amine content in terms of the number of tertiary aminescompared to overall molecular weight. It is believed that the higher thetertiary amine content the more rapid the catalytic activity in thepolyurethane art.

It would therefore be a substantial advance in the art if a new class ofamine catalysts were discovered which overcome some of the justenumerated disadvantages of the prior art.

SUMMARY OF THE INVENTION

A new class of compounds has been discovered which have been founduseful as polyurethane catalyst. These compounds have the followingstructural formula ##STR2## where R" is lower alkyl, R is hydrogen orlower alkyl and Y is selected from the group consisting of CN, CONH₂,CO₂ R', CONR'₂ and COR' where R' independently is hydrogen, lower alkylor aryl. Preferably R" contains 1-4 carbon atoms.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The compounds here may be prepared by resort to a wide variety ofsynthetic techniques. However, preferably these compositions areprepared by first making bis(dialkylaminopropyl)-amine. The bis-amineagain may also be prepared by a variety of known techniques. However,one excellent mode of preparation involves a reaction of a dialkylaminesuch as dimethylamine with acrylonitrile followed by hydrogenation ofthe resultant condensate to produce dimethylaminopropylamine. Inproducing dimethylaminopropylamine, one also produces thebis-dimethylaminopropylamine compound, which may be removed from themonomolecule by conventional means such as distillation and the like.

The bis-amine then readily reacts with a variety of monomers of the typeCH₂ ═ CHRY where R and Y have a significance as above discussed. Typicalreactants of this type include acrylamide, acrylonitrile, acrylic acid,and lower alkyl or aryl esters thereof, N,N-disubstituted acrylamidederivatives, and vinylketones such as methyl vinyl ketone, etc.

Most preferred compounds are those where R" in the above formula in bothinstances is methyl. Thus, greatly preferred compositions have theformula

    ((CH.sub.3).sub.2 NCH.sub.2 CH.sub.2 CH.sub.2).sub.2 NX

where X =

1. ch₂ ch₂ cn

2. ch₂ ch₂ conh₂

3. ch₂ ch₂ co₂ ch₃

4. ch₂ ch₂ cho

5. ch₂ ch₂ co₂ h

6. ch₂ ch₂ coch₃

7. ch₂ ch(ch₃)y

where Y = CN, CO₂ CH₃, CO₂ H, CONH₂, CHO

8. ch₂ ch₂ co₂ r

where R = R' or

9. CH₂ CH₂ CON(R,R')

R ≠ r', and they are alkyl, aryl, or H.

10. ch₂ chr"co₂ r

where R" = CH₃, Et, and R and R' as above.

11. CH₂ CHR"CON(RR')

The compounds here possess a number of useful characteristics makingthem exceptionally attractive as polyurethane catalysts. For example,the just defined compounds have a high tertiary amine content andresultant rapid catalytic activity in the polyurethane foam area.Tertiary amine content is calculated as the number of tertiary aminesdivided by the molecular weight times 1,000. For example, theacrylonitrile adduct of bis-(dimethylaminopropyl)-amine has a tertiaryamine content of 12.48 meq/g. In addition, the compounds here are alsorelatively nonvolatile and possess little if any odor. With respect tothe products, there are no solids handling problems such as are presentwith well known polyurethane catalysts as triethylenediamine. Thecatalysts of the invention are particularly desirable in foamingurethanes in that they provide a sufficient delay in the foamingoperation to aid in processing. Yet the catalysts also give good foamswith desirable tack-free times. As noted above this delay time isparticularly desirable in molding applications to allow sufficient timeto situate the prefoam mix in the mold. Lastly, the compounds are easilyprepared as typically described above, and are relatively inexpensive.

To prepare polyurethanes using the catalysts here, any aromaticpolyisocyanate may be used. Typical aromatic polyisocyanates includem-phenylene diisocyanate, p-phenylene diisocyanate, polymethylenepolyphenylisocyanate, 2,4-toluene diiocyanate, 2,6-tolylenediisocyanate, dianisidine diisocyanate, bitolylene diisocyanate,naphthalene-1,4-diisocyanate, diphenylene-4,4'-diisocyanate,aliphatic-aromatic diisocyanates, such as xylylene-1,4-diisocyanate,xylylene-1,4-diisocyanate, xylylene-1,3-diisocyanate,bis(4-isocyanatophenyl) methane, bis(3-methyl-4-isocyanatophenyl)methane, and 4,4'-diphenylpropane diisocyanate.

Greatly preferred aromatic polyisocyanates used in the practice of theinvention are 2,4- and 2,6-toluene diisocyanates and methylene-bridgedpolyphenyl polyisocyanate mixtures which have a functionality of fromabout 2 to about 4. These latter isocyanate compounds are generallyproduced by the phosgenation of corresponding methylene bridgedpolyphenyl polyamines, which are conventionally produced by the reactionof formaldehyde and primary aromatic amines, such as aniline, in thepresence of hydrochloric acid and/or other acidic catalysts. Knownprocesses for preparing the methylene-bridged polyphenyl polyamines andcorresponding methylene-bridged polyphenyl polyisocyanates therefrom aredescribed in the literature and in many patents, for example, U.S. Pat.Nos. 2,683,730; 2,950,263; 3,012,008; 3,344,162; and 3,362,979.

Most preferred methylene-bridged polyphenyl polyisocyanate mixtures usedhere contain from about 20 to about 100 weight percent methylenediphenyldiisocyanate isomers with the remainder being polymethylenepolyphenyl diisocyanates having higher functionalities and highermolecular weights. Typical of these are polyphenyl polyisocyanatemixtures containing about 20 to 100 weight percent methylenediphenyldiisocyanate isomers, of which 20 to about 95 weight percentthereof is the 4,4'-isomer with the remainder being polymethylenepolyphenyl polyisocyanates of higher molecular weight and functionalitythat have an average functionality of from about 2.1 to about 3.5. Theisocyanate mixtures are known commercially available materials and canbe prepared by the process described in U.S. Pat. No. 3,362,979, issuedJan. 9, 1968 to Floyd E. Bentley.

The hydroxyl-containing polyol component which reacts with theisocyanate may suitably by a polyester polyol or a polyether polyolhaving a hydroxyl number ranging from about 700 to about 25, or lower.When it is desired to provide a flexible foam, the hydroxyl number ispreferably in the range from about 25 to 60. For rigid foams, thehydroxyl number is preferably in the range from 350 to 700. Semi-rigidfoams of a desired flexibility are provided when the hydroxyl number isintermediate to the ranges just given.

When the polyol is a polyester, it is preferable to use, as thepolyester, a resin having a relatively high hydroxyl value and arelatively low acid value made from the reaction of a polycarboxylicacid with a polyhydric alcohol. The acid component of the polyester ispreferably of the dibasic or polybasic type and is usually free ofreactive unsaturation, such as ethylenic groups or acetylenic groups.The unsaturation, such as occurs in the rings of such aromatic acids asphthalic acid, terephthalic acid, isophthalic acid, or the like, isnon-ethyleneic and nonreactive. Thus, aromatic acids may be employed forthe acid component. Aliphatic acids, such as succinic acid, adipic acid,sebacic acid, azelaic acid, etc., may also be employed. The alcoholcomponent for the polyester should preferably contain a plurality ofhydroxyl groups and is preferably an aliphatic alcohol, such as ethyleneglycol, propylene glycol, dipropylene glycol, diethylene glycol,glycerol, pentaerthyritol, trimethyloethane, trimethylolpropane,mannitol, sorbitol, or methyl glucoside. Mixtures of two or more of theabove identified alcohols may be employed also if desired. When aflexible urethane foam is desired, the polyol should preferably have anaverage functionality of from about 2 to about 4 and a molecular weightof from about 2,000 to about 4,000. For rigid foams, the functionalityof the polyol component is preferably from about 4 to about 7.

When the hydroxyl-containing component is a polyether polyol for use inflexible polyurethane foam, the polyol may be an alkylene oxide adductof a polyhydric alcohol with a functionality of from about 2 to about 4.The alkylene oxide may suitably be ethylene oxide, propylene oxide, or1,2-butylene oxide, or a mixture of some or all of these. The polyolwill suitably have a molecular weight within the range of from about2000 to about 7000. For flexible polyether polyurethane foams, thealkylene oxide is preferably propylene oxide or a mixture of propyleneoxide and ethylene oxide.

For rigid polyether polyurethane foams, the polyol should have afunctionality of from about 4 to about 7 and a molecular weight of fromabout 300 to about 1200. Polyols for rigid polyether polyurethane foamsmay be made in various ways including the addition of an alkylene oxideas above to a polyhydric alcohol with a functionality of from 4 to 7.These polyols may also be, for example, Mannich condensation products ofa phenol, an alkanolamine, and formaldehyde, which Mannich condensationproduct is then reacted with an alkylene oxide. See U.S. Pat. No.3,297,597.

The amount of hydroxyl-containing polyol compound to be used relative tothe isocyanate compound in both polyester and polyether foams normallyshould be such that the isocyanato groups are present in at least anequivalent amount, and preferably, in slight excess, compared with thefree hydroxyl groups. Preferably, the ingredients will be proportionedso as to provide from about 1.05 to about 1.5 mol equivalents ofisocyanato groups per mol equivalent of hydroxyl groups. However, forcertain shock absorbing foams we have found that by using the catalystsof our invention the mol equivalents of isocyanate to hydroxy groups canbe as low as 0.4.

When water is used, the amount of water, based on the hydroxyl compound,is suitably within the range of about 0.05 to about 5.0 mol per molequivalent of hydroxy compound.

It is within the scope of the present invention to utilize anextraneously added inert blowing agent such as a gas or gas-producingmaterial. For example, halogenated low-boiling hydrocarbons, such astrichloromonofluoromethane and methylene chloride, carbon dioxide,nitrogen, etc., may be used. The inert blowing agent reduces the amountof excess isocyanate and water that is required in preparing flexibleurethane foam. For a rigid foam, it is preferable to avoid the use ofwater and to use exclusively the extraneous blowing agent. Selection ofthe proper blowing agent is well within the knowledge of those skilledin the art. See for example U.S. Pat. No. 3,072,082.

The catalysts discovered here are useful in the preparation of rigid orflexible polyester or polyether polyurethane foams based on the combinedweight of the hydroxyl-containing compound and polyisocyanate, areemployed in an amount of from about 0.05 to about 4.0 weight percent.More often that the amount of catalyst used is 0.1-1.0 weight percent.

The catalysts of this invention may be used either alone or in a mixturewith one or more other catalysts such as other tertiary amines or withan organic tin compound or other polyurethane catalysts. The organic tincompound, particularly useful in making flexible foams may suitably be astannous or stannic compound, such as a stannous salt of a carboxylicacid, a trialkyltin oxide, a dialkyltin dihalide, a dialkyltin oxide,etc., wherein the organic groups of the organic portion of the tincompound are hydrocarbon groups containing from 1 to 8 carbon atoms. Forexample, dibutyltin dilaurate, dibutyltin diacetate, diethyltindiacetate, dihexyltin diacetate, di-2-ethylhexyltin oxide, dioctyltindioxide, stannous octoate, stannous oleate, etc., or a mixture thereof,may be used.

Such other tertiary amines include trialkylamines (e.g. trimethylamine,triethylamine), heterocyclic amines, such as N-alkylmorpholines (e.g.,N-methylmorpholine, N-ethylmorpholine, etc.), 1,4-dimethylpiperazine,triethylenediamine, etc., aliphatic polyamines, such asN,N,N'N'-tetramethyl-1,3-butanediamine.

Conventional formulation ingredients are also employed, such as, forexample, foam stabilizers also known as silicone oils or emulsifiers.The foam stabilizer may be an organic silane or siloxane. For example,compounds may be used having the formula:

RSi[O--(R₂ SiO)_(n) --(oxyalkylene)_(m) R]₃ wherein R is an alkyl groupcontaining from 1 to 4 carbon atoms; n is an integer of from 4 to 8; mis an integer of 20 to 40; and the oxyalkylene groups are derived frompropylene oxide and ethylene oxide. See, for example, U.S. Pat. No.3,194,773.

In preparing a flexible foam, the ingredients may be simultaneously,intimately mixed with each other by the so-called "one-shot" method toprovide a foam by a one-step process. In this instance, water shouldcomprise at least a part (e.g., 10% to 100%) of the blowing agent. Theforegoing methods are known to those skilled in the art, as evidenced bythe following publication: duPont Foam Bulletin, "Evaluation of SomePolyols in One-Shot Resilient Foams", Mar. 22, 1960.

When it is desired to prepare rigid foams, the "one-shot" method or theso-called "quasi-prepolymer method" is employed, wherein thehydroxyl-containing component preferably contains from about 4 to 7reactive hydroxyl groups, on the average, per molecule.

In accordance with the "quasi-prepolymer method", a portion of thehydroxyl-containing component is reacted in the absence of a catalystwith the polyisocyanate component in proportions so as to provide fromabout 20 percent to about 40 percent of free isocyanato groups in thereaction product, based on the polyol. To prepare a foam, the reaminingportion of the polyol is added and the two components are allowed toreact in the presence of catalytic systems such as those discussed aboveand other appropriate additives, such as blowing agents, foamstabilizing agents, fire retardants, etc. The blowing agent (e.g., ahalogenated lower aliphatic hydrocarbon), the foam-stabilizing agent,the fire retardant, etc., may be added to either the prepolymer orremaining polyol, or both, prior to the mixing of the component, wherebyat the end of the reaction a rigid polyurethane foam is provided.

Urethane elasomers and coatings may be prepared also by known techniquesin accordance with the present invention wherein a tertiary amine ofthis invention is used as a catalyst. See, for example, duPont BulletinPB-2, by Remington and Lorenz, entitled "The Chemistry of UrethaneCoatings".

The invention will be illustrated further with respect to the followingspecific examples, which are given by way of illustration and not aslimitations on the scope of this invention.

EXAMPLE 1

To a 500 ml reactor equipped with a stirrer, thermometer and nitrogenatmosphere was charged 187 g of bis-(dimethylaminopropyl)-amine (BDMAPA)and 103 g of isopropanol. Acrylonitrile, 64 g, was added and thesolution was refluxed 1 hour, then 8 g more acrylonitrile was added.Reflux was continued 2 hours, then excess acrylonitrile and isopropanolwere distilled overhead. A vacuum of 0.8 mm was applied for 0.5 hours toremove traces of volatiles, and the product was recovered inquantitative yield. Its identity asN-cyanoethyl-N,Nbis-(dimethylaminopropyl)-amine was confirmed byinfrared and nmr spectroscopy. The flash point of this compound wasdesirably high, 190° F.

EXAMPLE 2

To an apparatus similar to that used in Example 1 was charged 112 g ofBDMAPA. Dropwise addition of 86 g of a 50% solution of acrylamideproduced a moderate exotherm. After the addition the mixture was heatedat 50° to 60° C. for 3 hours. The water was removed by benzene azeotropefollowed by vacuum application at 0.4 mm of mercury for 2 hours. Theproduct was recovered in quantitative yield and had no detectable odor.IR and NMR spectroscopy confirmed the identity of the compound as3-(bis-(dimethylaminopropyl)amino)propionaide.

EXAMPLE 3

This example illustrates the utility of the catalysts here in a flexibleurethane formulations. A high speed stirrer was used to mix 48.4 partsof toluene diisocyanate with the following blend of components:

    ______________________________________                                        THANOL®F-3520 Polyol.sup.(1)                                                                   100     parts                                            Water                4       parts                                            Silicone surfactant  1       part                                             Tin catalyst         0.6     parts                                            Test catalyst        0.1     parts                                            ______________________________________                                    

The blended components were poured into a standard mold and allowed torise. The observed properties are recorded below:

    ______________________________________                                                              Cream   Rise                                                                  time    time Foam                                       Expt.  Test Catalyst  (sec)   (sec)                                                                              Appearance                                 ______________________________________                                        1      Catalyst - Example 1                                                                         12      100  Good                                        2*    Catalyst - Example 1                                                                         --      83   Good                                       3      Catalyst - Example 2                                                                         13      97   Good                                         4**  Catalyst - Example 2                                                                         --      85   Good                                       ______________________________________                                         .sup.(1) A glycerine based polyether polyol of 3500 molecular weight          containing 15% ethylene oxide available from Jefferson Chemical Co.,          Houston, Texas.                                                               *0.13 parts catalyst used.                                                    **0.2 parts catalyst used.                                               

EXAMPLE 4

Here the catalyst of Example 1 was employed in another formulation toproduce a packaging foam. The formulation was as follows:

    ______________________________________                                        Foam Ingredients           Parts                                              ______________________________________                                        THANOL® SF-2750.sup.(1)                                                                              100                                                Water                      20                                                 Chlorotrifluoromethane blowing agent                                                                     35                                                 Silicone surfactant        1.5                                                Catalyst, Example 1        3.0                                                T-12                       0.02                                               MONDUR® MR Polyisocyanate.sup.(2)                                                                    140.5                                              NCO/OH                     0.4                                                Details                                                                       Cream time, sec.           ˜12                                          Rise time, sec.            ˜50                                          Gel time, sec.             ˜55                                          ______________________________________                                         .sup.(1) A packaging foam polyol available from Jefferson Chemical Co.        Inc., Houston, Texas.                                                         .sup.(2) Polyphenylmethylene polyisocyanate of average functionality of       2.7, a product of Mobay Chemical Corp.                                   

As can be seen above cream, rise and gel times are all acceptable.

EXAMPLE 5

This example illustrates use of the urethane catalysts here in a rigidurethane formulation. The components below were blended with a highspeed stirrer, then poured into a standard mold and allowed to rise.

    ______________________________________                                        MONDUR® MR polyisocyanate                                                                          46.6 parts                                           2500 parts THANOL® RS-700 polyol.sup.(1)                                   34 parts silicone surfactant                                                                          52.4 parts                                            880 parts fluorocarbon blowing agent                                         Catalyst tested           1.0 part                                            .sup.(1) A nine mol propoxylate of sorbitol.                                  The rise characteristics observed were recorded below:                                      Cream time Tack free  Rise time                                 Catalyst tested                                                                             (sec)      time (sec) (sec)                                     ______________________________________                                        Catalyst - Example 1                                                                        40         145        150                                       Catalyst - Example 1*                                                                       35         110        120                                       Catalyst - Example 2                                                                        41         140        150                                       Catalyst - Example 2*                                                                       37         105        120                                       ______________________________________                                         *1.25 parts catalyst used.?                                              

We claim:
 1. A compound of the formula: ##STR3## where R" is loweralkyl, R is hydrogen or lower alkyl and Y is CONR'₂ where R' isindependently hydrogen, lower alkyl or aryl.